Single crystals of a semi-organic nonlinear optical (NLO) material, L-proline cadmium chloride monohydrate (L-PCCM), were grown by the slow evaporation and slow cooling method. The synthesized material was purified by repeated recrystallization. The grown crystals were transparent and had dimensions 16 × 8 × 5 mm3; they were characterized by single-crystal XRD, FT-IR, CHN analysis, density, melting point measurements, and UV-vis-NIR techniques. The SHG efficiency of L-PCCM is twice that of potassium dihydrogen phosphate (KDP).

We report on the production of organic single crystalline thin films for integrated nonlinear optical applications by a vapor growth technique. The configurationally locked polyene chromophore 2-{3-[2-(4-dimethylaminophenyl)vinyl]-5,5-dimethylcyclohex-2-enylidene} malononitrile (DAT2) that was used exhibits a noncentrosymmetric crystalline arrangement with monoclinic point group symmetry 2. It shows a second harmonic generation signal of about 2 orders of magnitude greater than that of urea. The grown DAT2 films are single crystalline and exhibit good optical quality and suitable size (area of ~5 × 3 mm2 and the thickness in the range of 0.2-5 m) for fabrication of photonic devices. Growth rates of a few hours have been achieved. Furthermore, the edges of the films are sharp and flat, which greatly reduces the additional processing requirements for applications.

Amino acid family crystals exhibit excellent nonlinear optical and electrooptical properties. L-Alanine single crystal belongs to the amino acid group and has been grown by the slow evaporation solution growth technique at room temperature. The grown crystals were characterized by high-resolution X-ray diffractometry (HRXRD), nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, UV-Vis, Raman spectroscopy, mass spectra analyses and density measurements. Its laser damage threshold was measured and its nonlinear optical response was tested by using a Q-switched Nd:YAG laser, and the value of laser damage threshold is greater than that of potassium dihydrogen phosphate (KDP).

The crystal structure of the nonlinear optical material, iodoform octasulfur (CHI3·(S8)3), in the polar space group R3m, has been shown to contain three unique S···I and several S···S close contacts ( 4.0 Å), that fall well below the sum of the van der Waals radii of the two atoms concerned. These interactions have all been characterized topologically following the multipole refinement of the crystal structure of iodoform octasulfur. The natures of the possible charge transfer (S···I) and electrostatic (S···S) interactions in this molecule have been investigated based on charge density studies. The properties of the electron density at the bond critical points provide a tool for determining which of the sulfur or iodine atom acts as the donor and which acts as the acceptor in each of the possible S···I charge-transfer interactions present in this molecule. This all leads to a better understanding of the donor/acceptor nature for both types of atoms in charge-transfer complexes of inorganic nonlinear optical materials. The analysis of the structure of iodoform octasulfur has also provided new insight into the relationship between charge density studies and VSEPR theory.